Originally Posted by corporate-wage-slave

If it's an NHS or NHS Scotland vaccine certificate, there is an option to download it. But don't worry too much, so long as you have had either 2 primary doses of the vaccine or the Janssen single dose then you can do it all at the airport at check-in, it just takes a few extra minutes. The advantage of doing it in advance - via uploading (Salesforce) or VeriFLY - is to get it out of the way and to faciliate OLCI. But if you can't or prefer not to do that, just do it at the airport. They give you a barcode to do the attestation. You would be doing this three days before departure or after.

Salesforce link:
digitalboarding.force.com

and see the the VeriFLY and Salesforce threads for more information and data points.